It's so very very sad, and as said, we don't exactly know why the Head did this. OFSTED can't be blamed for everything. If they found shortcomings, or if other staff members lodged concerns, OFSTED has to report it and act. The safeguarding checks were not correct in this instance, and that reflects very poorly on the senior management. Yes, the buck stops there, and it has to be referred.
I know a school's inspector, (very well infact), and every time he enters an inspection it is with a kind and supportive attitude. Occasionally a Head might break down in tears due to all kinds of reasons.